Arrange the following carbanions in order of their decreasing stability.

A. H3C-CC-

B. H-CC-

C. H3C-CH-2

1. A>B>C

2. B>A>C

3. C>B>A

4. C>A>B

Hint: As the percentage of s character increases electronegativity of carbon increase
+I effect decreases the stability of carbon anion. Since CH3- group has + I-effect, therefore, it intensifies the negative charge and hence destabilises (A) relative to (B). sp hybridised carbanion is more stabilised than sp3 hybridized carbanion.
Thus, the stability order is as follows:
Hence, B>A>C